Descriptive statistics of the study sample for 2006 (<i>N</i> = 25,309) and 2009 (<i>N</i> = 31,783) respectively.

*The distribution in 2009 is different from the distribution in 2006 with P≤0.05, two-sided. Generalized linear mixed models, corrected for neighborhood-level clustering effects.2009年的分布与2006年的分布存在统计学差异（双侧检验，P≤0.05）。本次分析采用广义线性混合模型（Generalized linear mixed models），对街区层面的聚类效应进行了校正。